Project Summary/Abstract There continues to be an urgent need to increase the effectiveness of behavioral counseling for promoting long-term smoking cessation. Research on positive psychology has been growing rapidly over the past two decades and provides a valuable perspective for developing novel and more effective approaches to addictions treatment that are likely to have broad appeal. Building from a substantial body of research on positive psychology interventions for increasing positive affect and reducing stress and depression, we recently developed and pilot tested a treatment called Positive Psychotherapy for Smoking Cessation (PPT-S). PPT-S is designed to harness personal strengths to assist smoking cessation, to enhance focus on the mental health benefits of quitting smoking, and to increase the frequency of and the attention to positive experiences and cognitions during quitting. In a pilot randomized controlled trial, PPT-S resulted in greater odds of smoking abstinence over 6 months of follow-up compared to a time-matched control condition. We also found that greater engagement in PPT-consistent strategies was associated with increased odds of abstinence over time, that those with higher baseline positive affect engaged in more PPT-consistent strategies, and that the efficacy of PPT-S was greatest at higher levels of positive affect. Results show the potential promise of PPT-S and suggest that increasing engagement in PPT-consistent behavioral and cognitive strategies, especially for those with low positive affect, may further enhance the efficacy of this approach. Towards this end, we have developed an enhanced version of PPT-S (PPT-S+) that uses text messaging to provide PPT-related content and to prompt daily engagement in PPT-consistent strategies; pilot testing indicates high acceptability of this approach with participants responding to over 80% of daily interactive text messages. The overall objective of the proposed project is to conduct a randomized controlled trial to test the efficacy of PPT-S+. Specifically, we will randomize 340 smokers to either PPT-S+ or a time-matched standard behavioral smoking cessation treatment plus text messaging (ST+). Both treatment conditions will include nicotine replacement therapy and a text-messaging intervention for smoking cessation. We will test the hypotheses that PPT-S+ will result in superior smoking outcomes compared to ST+ and that this effect will be mediated by greater engagement in PPT-consistent strategies, increased self-efficacy for quitting smoking, and reduced residual attraction to smoking. We also will examine whether the effect of PPT-S+ remains stronger for those with higher baseline positive affect even when text messaging is utilized to increase treatment engagement. This project can have significant public health impact by establishing the efficacy of a highly innovative approach to improving behavioral smoking cessation counseling, which can be readily implemented and is likely to appeal to a broad range of smokers due to its emphasis on personal strengths and enhancing overall well-being and happiness.